**4.3 Characterization of the gold nanoparticles and seeded silica**

The GNPs were analyzed under a TEM. **Figure 10** illustrates the GNPs with a diameter of 7 ± 3 nm and spherical shape overall.

The seeding process was followed with 2 h of still time as well as with 30 min of still time. The first and second samples were observed under the microscope. The samples were taken with the purpose of observing the development of the seeds. **Figure 11a** presents an SEM image of seeded silica with 30 min of resting time, while **Figure 11b** presents an SEM image of seeded silica with 2 h of resting time. The images show that 30 min is enough time to create the seeds because both images display approximately the same number of nucleus per silica particle.

Even though a complete shell was not formed, the seeds are ready to grow the gold shell on the next step. A TEM image of a seeded silica particle is presented in **Figure 12**. This image corroborates the seeding process as well as the silica functionalization.
